Hello emergency99, I just want to remind you of this hint.

OK - you can alsou use this link
http://fahrplan.oebb.at/bin/query.exe/dn?
to query the route.

…furthermore the tunnels maxheight in the Lehnergasse is 2.5 meter – to low for a bus.

Wolfgang

Hello emergency99,
you wrote:
"According to VOR-Webpage, the bus 703 at 16:04 goes up here. Is it really a oneway?"

Look here:
http://fahrplan.oebb.at/bin/query.exe/dn?ld=21&seqnr=3&ident=dl.024287178.1564687959&moreDetail=1&#moreC0-0

Wolfgang